everywhere goes on from long continuous observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work."
It is a fact that the increase in the birth of animals is greater than the existing food permits of sustaining. There is no exception to the rule that all organic beings tend to increase so rapidly that our earth would be overrun very soon by the offspring of a single pair, were these not destroyed. It is for this reason that a struggle for existence must arise. Every animal tries to live, does its best to eat, and seeks to avoid being eaten by others. With its particular peculiarities and weapons it struggles against the entire antagonistic world, against animals, cold, heat, dryness, inundations, and other natural occurrences that may threaten to destroy it. Above all, it struggles with the animals of its own kind, who live in the same way, have the same peculiarities, use the same weapons and live by the same nourishment. This struggle is not a direct one; the hare does not struggle directly with the hare, nor the lion with the lion—unless it is a struggle for the female—but it is a struggle for existence, a race, a competitive struggle. All of them can not reach a grown-up age; most of them are destroyed, and only those who win the race remain. But which are the ones to win in the race? Those which, through their peculiarities, through their bodily structures are best able to find food or to escape an enemy; in other words, those which are best adapted to existing conditions will survive. "Because there
